Hey mate,

the Volume generated by rotating a function f(x) about the x-axis between

x = a and b is given by

V = pi * int ( f(x)^2 dx , x = a to b )

here however you want to rotate about the y-axis, i.e.

V = pi * int (g(y)^2 dy , y = a1 to b1)

so you need to find the alternative form g(y) (hint rearrange y = 1 + sqrt(x) into the form x = g(y) ) and its altered bounds { hint a1 = f(a)...}

please post if you require any further help.