Answer:
The correct option is C: Jack could increase his utility by buying more pencils and fewer pens.
Step-by-step explanation:
The marginal rate of substitution or MRS is defined as the rate at which one gives up a reasonable amount of one product to exchange for another products, and still maintains the same utility level. For Jack to maintain the same level of utility, he needs to more pencil and fewer pens to maintain an equilibrium in his purchase of pens and pencils.