Consider an economy with two types of firms, S and I. S firms always move together, but I firms move independently of each other. For both types of firms, there is a 70% probability that the firm will have a 20% return and a 30% probability that the firm will have a -30% return. (c) The standard deviation for the return on an equally-weighted portfolio of 20 S firms is closest to: (1) 5.1% (2) 23% (3) 15% (4) 5.25% (d) The standard deviation for the return on an equally-weighted portfolio of 20 I firms is closest to: (1) 5.25% (2) 5.1% (3) 15% (4) 23%