The "Dogs of the Dow" are the stocks listed on the Dow with the highest dividend yield. The following table shows the top 10 stocks of the "Dogs of the Dow" list for 2015, based on their performance the preceding year. Symbol Company Price ($) Yield T AT&T 33.59 5.48% VZ Verizon 46.78 4.70% CVX Chevron 112.18 3.82% MCD McDonald's 93.70 3.63% PFE Pfizer 31.15 3.60% GE General Electric 25.27 3.48% MRK Merck 56.79 3.17% CAT Caterpillar 91.53 3.06% XOM ExxonMobil 92.45 2.99% KO Coca-Cola 42.22 2.89% You decide to make a small portfolio consisting of a collection of 6 of the top 10 Dogs of the Dow. (a) How many portfolios are possible? portfolios (b) How many of these portfolios contain MRK but not PFE? portfolios