[0.05(-$34 – $4.1)2 + 0.20(-$22 – $4.1)2 + 0.50($12 – $4.1)2 + 0.20($14 – $4.1)2 + 0.05($28 – $4.1)2]½
=[0.05(-38.10)2 + 0.20(-26.10)2 + 0.50(7.90)2 + 0.20(9.90)2 + 0.05(23.90)2]*0.5
=0.05*-38.10 + 0.20*-26.10 + 0.50*7.90 + 0.20*9.90 + 0.05*23.90
=0.05(-38.10+7.9+23.9)+0.20(-26.10+9.9)
=0.05(-38.10+31.8)+0.20(-16.2)
=0.05(-8.10+1+0.8)+-3.24
=0.05(-7.10+0.8)-3.24
=0.05(-6.3)-3.24
=-0.315-3.24
= -3.555 I suppose i have made an error but I cannot find it. 
$$\left({\mathtt{0.05}}{\mathtt{\,\times\,}}{\mathtt{\,-\,}}\left({\mathtt{38.1}}{\mathtt{\,\times\,}}{\mathtt{2}}\right){\mathtt{\,\small\textbf+\,}}{\mathtt{0.2}}{\mathtt{\,\times\,}}{\mathtt{\,-\,}}\left({\mathtt{26.1}}{\mathtt{\,\times\,}}{\mathtt{2}}\right){\mathtt{\,\small\textbf+\,}}{\mathtt{0.5}}{\mathtt{\,\times\,}}{\mathtt{7.9}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.2}}{\mathtt{\,\times\,}}{\mathtt{9.9}}{\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.05}}{\mathtt{\,\times\,}}{\mathtt{23.9}}{\mathtt{\,\times\,}}{\mathtt{2}}\right){\mathtt{\,\times\,}}{\mathtt{0.5}} = {\mathtt{0}}$$
$$\left({\mathtt{0.05}}{\mathtt{\,\times\,}}\left(-{\mathtt{38.1}}\right){\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.2}}{\mathtt{\,\times\,}}\left(-{\mathtt{26.1}}\right){\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.5}}{\mathtt{\,\times\,}}\left({\mathtt{7.9}}\right){\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.2}}{\mathtt{\,\times\,}}\left({\mathtt{9.9}}\right){\mathtt{\,\times\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.05}}{\mathtt{\,\times\,}}\left({\mathtt{23.9}}\right){\mathtt{\,\times\,}}{\mathtt{2}}\right){\mathtt{\,\times\,}}{\mathtt{0.5}} = {\mathtt{0}}$$
.