Answer
a. Σm= 77
b. Σf = 2116
c. Σmf = 662
d.Σm^{2}f = 11,734
Work Step by Step
a) $Σm = 5+10+17+20+25 = 77$
b) $Σf = 46, Σf^{2} = 2116$
c) $Σmf = (5\times12)+(10\times8)+(17\times6)+(20\times16)+(25\times4) = 60+80+102+320+100 = 662$
d) $Σm^{2}f = (5\times5\times12)+(10\times10\times8)+(17\times17\times6)+(20\times20\times16)+(25\times25\times4) = 300+800+1734+6400+2500 = 11,734$
