No able to get the results from the last segment

edit

I am giving my full code below. I am unable to get the results from code marked in red. Rest is working fine

html('<center><h2>Tyre Design</h2></b>by : Madan Saini')
#Input Parameters
PI = pi.n()
@interact(layout=[['t_size'],['od','sw'],['nsd','ut'],['bn','bg'],['pn','pg'],['rg','beta_c'],['rim_d','rim_w'],['rim_f'],['auto_update']])
def myplot(t_size=input_box('3.00-18',label='Tyre Size',width=20),od=input_box(round(627,2),label='Tyre Outer Dia.',width=20), sw=input_box(round(80,2),label='Tyre Section Width',width=20), nsd=input_box(round(6.5,2),label='Non Skid Depth',width=20), ut=input_box(round(2.5,2),label='Under Tread',width=20), bn=input_box(round(0,0),label='No of Breakers',width=20), bg=input_box(round(1.2,2),label='Breaker Gauge',width=20), pn=input_box(round(2,0),label='No of Plies',width=20), pg=input_box(round(0.85,2),label='Ply Gauge',width=20), rg=input_box(round(2.5,2),label='Side Rubber Gauge',width=20), rim_d=input_box(round(458.7,2),label='Rim Dia (D)',width=20), rim_w=input_box(round(65,0),label='Rim Width(A)', width=20),rim_f=input_box(round(14,2),label='Rim Flange Height(G)',width=20), beta_c=input_box(40,label='Crown Angle',width=20), auto_update=False):

#Initial guess: Assume the closest ellipse
    rc = ((od/2)-nsd-ut-(bn*bg)-(pn*pg/2))
    W = ((sw/2)-rg-(pn*pg/2))
    rb = ((rim_d/2)+rim_f-(pn*pg*1.5))
    zb = rim_w/2.0
    rw_init = rc*(rb/rc+sqrt(1-(zb/W)^2))/(1+sqrt(1-(zb/W)^2))
    rw = var('rw')
    Bc = var('Bc')
    def find_tire_width(data):
        rw = data[0]
        Bc = data[1]
        r = var('r')
        F = (r^2-rw^2)*sqrt(rc^2-r^2*sin(Bc)^2)/sqrt((rc^2-rw^2)^2*rc^2*cos(Bc)^2-(r^2-rw^2)^2*(rc^2-r^2*sin(Bc)^2))
        z = function('z',r)
        d2 = desolve_rk4(diff(z,r)+F,z,ics=[rc*0.9999,0],end_points=(rw-(rc-rw)/2),step=-(rc-rw)/2000)
        S = spline(d2)
        return [S(rw), S(rb)]

    Bc = (90-beta_c)/180*PI
    zwb = find_tire_width([rw_init, Bc])
    show("calculated rc = " + str(rc))
    show("calculated W = " + str(W))
    show("calculated rb = " + str(rb))
    show("calculated zb = " + str(zb))
    show("calculated Bc = " + str(Bc))    
    show("rw_init based on elliptical approximation = "+str(rw_init))
    show("zw in the natural shape = " + str(zwb[0]))
    show("zb in the natural shape = " + str(zwb[1]))

from this point the code is not showing any results

def f(input):
    zwb = find_tire_width(input)
    return ((W-zwb[0])^2+(zb-zwb[1])^2);

c1 = lambda input: input[0]-rb
c2 = lambda input: rc - input[0]
c3 = lambda input: input[1]
c4 = lambda input: pi/2 - input[1]
a = minimize_constrained(f,[c1, c2, c3, c4],[rw_init, Bc])
view(a)
show("rw in the optimal shape = " + str(a[0]))
show("Beta in the optimal shape = " + str(a[1]) + " radians")

please help me out to solve this issue..