13. Pencils sell for 10 cents and pens sell for 50 cents. Suppose Jack. whose preferences satisfy all of the basic assmnptions. buys 5 pens and one pencil each semester. With this consiunption bundle, his MRS of pencils for pens is 3. W hich of the following is true? (a) Jack could increase his utility by buying more pens and fewer pencils. (b Jack could increase his utility by buying more pencils and fewer pens. d (e Jack is at a corner solution and is maximizing his utility. ) c) Jack could increase his utility by buying more pencils and more pens. ) Jack could increase his utility by buying fewer pencils and fewer pens. )