A father decides to put his two sons to work landscaping. The business involves going to a customer's home and providing landscaping services (cut grass, edge sidewalk, pull weeds in flower beds, prune bushes and trees, rake leaves). Rather than paying a flat wage, the father decides to pay an incentive according to the following schedule (average across all lawns).
$$
\begin{array}{lclcc}
\hline & \begin{array}{c}
\text { Piece Rate Incentive } \\
\text { per Person }
\end{array} & \begin{array}{c}
\text { Physical Effort }
\end{array} & \begin{array}{c}
\text { Time to Complete } \\
\text { per Person }
\end{array} & \begin{array}{c}
\text { Charge to } \\
\text { Customer }
\end{array} \\
\text { Cut grass } & \$ 4 & \text { Easy } & .4 \mathrm{hr} & \$ 30 \\
\text { Edge sidewalk } & \$ 1 & \text { Easy } & .1 \mathrm{hr} & \$ 5 \\
\text { Pull weeds } & \$ 6 & \text { Very Hard } & .5 \mathrm{hr} & \$ 40 \\
\text { Prune bushes, etc. } & \$ 5 & \text { Hard } & .5 \mathrm{hr} & \$ 30 \\
\text { Rake leaves } & \$ 5 & \text { Hard } & .5 & \$ 25 \\
\hline
\end{array}
$$
At the end of the second week under this arrangement the boys are quarreling with each other and not happy with their dad. All of the disagreements revolve around the incentive system. What might be the problems?