17) Below are sales for five years:

Year	Winter	Spring	Summer	Fall
2010	18.6	23.5	20.4	41.9
2011	18.1	24.7	19.5	46.3
2012	22.4	28.8	21	45.5
2013	23.2	27.6	24.4	47.1
2014	24.5	31	23.7	52.8

The seasonal indices for Spring and Summer are:

0.73 and 0.93 b. 0.93 and 0.75 c. 0.93 and 0.16 d. 0.73 and 0.16