Surface area and volume of regular four-sided pyramid

Calculate the surface area and volume of regular four-sided pyramid if B = 36cm² and height 4 cm.

Solved:

B=36cm²        H=4cm                  M=4*a*h/2              P=M+B

B=√36            h²=H²+(a/2)²         M=4*6*5/2              P=60+36

B=6cm            h²=4²+(6/2)²         M=60cm²                 P=96cm²

a=6cm             h²=16+9

                        h=√25                  

                        h=5cm                  V=B*H/3

                                                     V=36*4/3

                                                     V=48cm²