How do I solve for b.?

FIGURE 2.4 The Changing Mix of Output In the twentieth century the total output of the U.S. economy increased thirteenfold. As the economy grew, the farm sector shrank and the manufacturing share of total output declined. Since 1930 the American economy has been predominantly a service economy, with output and job growth increasingly concentrated in retail trade, education, health care, entertainment, personal and business services, and government. THE MIX OF OUTPUT IN 1900 THE MIX OF OUTPUT IN 2000 Manufacturing 22% Government 10% Farming 2% Construction and mining 6% Government 18% Services 22% Farming 37% Manufacturing 20% Construction and Services 54% mining 9% Source: U.S. Departments of Commerce and Labor. According to the figure, a. Between 1900 and 2000, the quantity of manufactured output increased b. By how much (in percentage terms)? ...: Hint: Assume that total output in 1900 = $100. (Use the percentage change formula = [(new value - original value)/original value]*100.) c. During that time, the manufacturing share of GDP fell