Advertising the price of products.
a. decreases
c. increases
b. has no effect

Advertising B. HAS NO EFFECT on the price of products.

It has an effect on the demand of the products. If your product is well advertised, a lot of people will know about it and will be encouraged to buy said product.

Direct factors that affect the price of the products are the costs of direct materials, labor, and factory overhead. 

Demand may also factor-in on the price of the supply. If the supply is limited and demand is high, the price is high. If supply is plentiful and demand is low, the price is low.

The correct answer is (b) the marginal contribution of labor decreases as the quantity of labor used in production increases;