Take into account that the volume of rectangular prism is given by:
Volume = height x length x width
in this case you have:
height = a²b
length = ab³
width = ab²
replace the previous algeraic expressions into the formula for the volume V, and simlpify by using properties of exponents:
V = (a²b)(ab³)(ab²)
V = a⁴b⁶
Hence, the expression for the volume of the given rectangular prism is a⁴b⁶