Answer
$μ=27.86~years$
$σ=6.36~years$
Work Step by Step
$x_1=First~Class~Midpoint=12.5$
$x_2=Second~Class~Midpoint=17.5$
$x_3=Third~Class~Midpoint=22.5$
$x_4=Fourth~Class~Midpoint=27.5$
$x_5=Fifth~Class~Midpoint=32.5$
$x_6=Sixth~Class~Midpoint=37.5$
$x_7=Seventh~Class~Midpoint=42.5$
$x_8=Eighth~Class~Midpoint=47.5$
$μ=\frac{Σx_if_i}{Σf_i}=\frac{12.5\times7.0+17.5\times488.5+22.5\times1172.1+27.5\times1298.2+32.5\times1035.3+37.5\times544.0+42.5\times116.6+47.5\times7.3}{4669}=27.86$
$σ=\sqrt {\frac{(x_i-μ)^2f_i}{Σf_i}}=\sqrt {\frac{(12.5-27.86)^2\times7.0+(17.5-27.86)^2\times488.5+(22.5-27.86)^2\times1172.1+(27.5-27.86)^2\times1298.2+(32.5-27.86)^2\times1035.3+(37.5-27.86)^2\times544.0+(42.5-27.86)^2\times116.6+(47.5-27.86)^2\times7.3}{4669}}=6.36$
