The portion of the tangent at any point on the curve x=at3, y=at4 between the axes is divided by the abscissa of the point of contact externally in ratio
34
dydx=4t3
Tangent is y−at4=4t3(x−at3)
x - intercept =at34 and y - intercept =−at43
The point of intersection of tangent with the axes are (at34, 0) and (0, −at43)
=mn=−34
Hence the correct option is (b)