I need help with the following problem.
Given a pyramid ABCDM. The opposite planes (ABM) and (DCM) are perpendicular to the base ABCD. The base ABCD is trapezoid (AD || BC) and AD=3 cm., BC=5 cm. If the area of the triangles ABM and BCM is $20 cm^2 $ and $9 cm.^2$, find the volume of the pyramid ABCDM.