Provide an example of function f:R --> R and g:R--> R, and c is subset to R, such that g is not differentiable at c and fog is defferentiable at c.

Provide an example of function f:R --> R and g:R--> R, and c is subset to R,

such that f is not differentiable at g(c) and fog is defferentiable at c.

Provide an example of function f:R --> R and g:R--> R, and c is subset to R,

such that f+g is differentiable at c and f is not defferentiable at c.

it kind of makes me confused