Identify the variation as direct, inverse, joint or combined. l=cmn

The variation is joint variation.

Step-by-step explanation:

The given equation is,

where

c is the proportionality constant.

So,

This can be segregated as,

and

Therefore, I is in direct variation with m and n separately. But as both variations are of same type, so I is in joint variation with m and n.

b) well because you get well