Using the Following Excerpts from the Most Recent Annual Report

Using the following excerpts from the most recent annual report of WooHoo, a high technology firm, analyze the accounts receivable and allowance for doubtful accounts.Be sure to show all calculations and write a thorough interpretation of those calculations.
$$\begin{array} {| l | r r| } \hline \text { (dollars in millions) } & 2015 & 2014 \\\hline \text { Net sales } & \$ 7,200 & \$ 6,400 \\\text { Accounts receivable - less allowance for doubtful accounts of } & \$ 1,000 & \$ 1,030 \\\$ 22 \text { at April } 30,2015 \text { and } \$ 40 \text { April } 30,2014 &\\\hline\end{array}$$ WooHoo
Valuation And Qualifying Accounts
For the Years Ended April 30, 2015, 2014 and 2013
$$\begin{array} { | l | r | r | r | r | } \hline & \begin{array} { c } \text { Balance at } \\\text { beginning of } \\\text { period }\end{array} & \begin{array} { c } \text { Charged to } \\\text { expenses }\end{array} & \text { Deductions } & \begin{array} { c } \text { Balance at } \\\text { end of period }\end{array} \\\hline \begin{array} { l } \text { Allowance for } \\\text { doubtful accounts }\end{array} & & & & \\\hline 2015 & \$ 40 & \$ 5 & \mathbf { ( \$ 2 3 ) } & \$ 22 \\\hline 2014 & \$ 51 & \$ 4 & \mathbf { ( \$ 1 5 ) } & \$ 40 \\\hline 2013 & \$ 46 & \$ 25 & \mathbf { ( \$ 2 0 ) } & \$ 51 \\\hline\end{array}$$