Please explain the thought process behind it, its more important to me than the answer. Thank you. Also what exactly is a colon is pseudo code?

Consider the following pseudocode, where procedures Q and R are nested inside procedure P: procedure P (A, B: real) X: real procedure Q (B,C: real) Y: real procedure R (A,C: real) Z: real Assuming static scope, what is the referencing environment (i.e., what names are known, and what do they refer to) at the location marked by (*)