Define a Haskell function named addUs that adds $2$ input numbers. Using this function as a building block, define a Haskell function multiplyUs that multiplies two input numbers. The multiplyUs function should cater to the following:

Inputs may be signed numbers, e$.$g$.,$ multiplyUs $(-2)(3)$ should result in $-6,$ and multiplyUs $(-2)(-6)$ should result in $12.$

It should use guard expressions and recursion.

There is no need to write the main function to perform user interaction. Writing the definition for addUs and multiplyUs is sufficient.

Explain the type signature for your code.