Parallel structure in a series

Is this sentence correct?

Customers should use the web as a cost-effective support mechanism to make inquiries about products and services, to place orders, receive technical assistance and to resolve issues.
a. yes
b. no

Answer: b

Explanation: Elements in a series must have the same grammatical (parallel) structure.

Correction: Customers are encouraged to use the web as a cost-effective support mechanism to make inquiries about products and services, to place orders, to receive technical assistance and to resolve issues.