How do I use substitution to solve these integrals?

[Physics Help!]

Please help me calculate these integrals.
Suppose that ∫f(t)dt=11 [0,1]. Calculate each of the following.
A. ∫f(4t)dt [0,0.25] =

B. ∫f(1−4t)dt [0,0.25] =

C. ∫f(3−8t)dt [0.25,0.375] =

I did the first one and I believe is right and I try to do the 2nd and 3rd one similarily and can't get them .
u=4t
du=4dt, or
dt=(1/4)du
∫f(4t)dt [0,0.25]
=∫f(u)(1/4)du [0,4*0.25]
=(1/4)∫f(u)du [0,1]
=(1/4)*11
=11/4

 

[micromass]

The second one is almost exactly the same. What substitution would you try??