need improvement with axis labels and heavy axis lines

poor eyes here, thanks

not like fortran, how to extend lines?

t = var('t')
y = function('y')(t)
ye = desolve(diff(y,t) == 2*10^(-5)*y*(1500-y), y, ics=[0,50])
ye = ye*3/100
yt = solve(ye.simplify_log(), y)
show(expand(yt))
P = plot((1500*e^(3/100*t)/(e^(3/100*t) + 29)),t,0,250, color='red', thickness = 10 )
L = line([(0,1500), (260,1500)], linestyle=":", color="grey", thickness = 10)
show(P+L, figsize=5)