Explanation
This formula is composed of two lookups for the same client. The first lookup finds the onsite rate for the client in column B and multiplies the result by the number of hours in column C:
=VLOOKUP(B5,rates,2,0)*C5
The second lookup finds the offsite rate for same client and multiplies the result by the number of hours in column D:
VLOOKUP(B5,rates,3,0)*D5
In the final step the two results are added together:
=(50*0)+(60*16)
=960