What is this modular arithmetic question asking exactly?

I just completed the first two parts of a question and am not sure how to use my answers in part c).

a) Write down an integer r which is divisible by 2611 and is congruent to 1 modulo 324

$\displaystyle r = 2611(-17) \equiv 1~mod~324$

b) Write down an insteger s which is divisble by 324 and is congruent to 1 modulo 2611

$\displaystyle s = 324(137) \equiv 1~mod~2611$

c) Consider the function $\displaystyle f : \mathbb{Z}_{845964}\rightarrow \mathbb{Z}_{2611}\times\mathbb{Z}_{324}$ given by:

$\displaystyle f(x~mod~845964)=(x~mod~2611,x~mod~324)$

Compute the value of $\displaystyle f(ar+bs)$

d)Deduce that $\displaystyle f$ is onto.

Is it perhaps notation that I don't understand that is asking me to find an integer x that satisfies both congruence equations?