If a firm decides to pay out $100\%$ of income in dividend in year $1,$ the book value of equity to common holders in year $1$ should equal a$.$ Book value of equity to common holders in year $0$ b$.$ Book value of equity to common holders in year $0+$ comprehensive income in year $1$ c$.$ Book value of equity to common holders in year $0+$ required income in year $1$ d$.$ Required income in year $1$