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Stefani is ordering fertilizer for her garden. A local garden supply store sells fertilizer by the yard (that really means cubic yard, but that is what they call it).For every yard she orders there is a $\textbackslash$$15charge and ,in addition ,there is a $\textbackslash$$40 delivery charge. ( Total Cost =~$\textbackslash$$15(yard)+~$\textbackslash$$40.)  $\textasciitilde$  If the average order is 4.3 yards with standard deviation of 2.9 yards, what is the mean and standard deviation of the Total Cost of a typical order? 
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The correct answer is (c). When using a linear transformation (Total cost 15 (yard)+40), the mean is changed by both the multiplication and addition. But the standard deviation is only changed by the multiplication. Mean = 15(4.3) +40=$\textbackslash$$ 104.50; =15(2.9) =~$\textbackslash$$43.50. 