1. Draw a cash flow (in present value) diagram that presents Cumulative Solar Savings and Mortgage Payment (i.e., the column for "principle balance" in Table 1), as a function of Time (Years, from Year 1 to Year 20). The pattern of these two curves should be similar to that for "loan balance" and "cumulative solar savings", as shown in Figure 1 below. Investment = loan + DP B. DP ( cumulative solar savings ($5) = LCS F. cumulative fuel savings (F-S) loan belance E. D (- ) Cash Flow (+) DP evaluation period Figure 1: For a given evaluation period n., there are numerous critical points in time that communicate concepts of "payback" for the client. The following shows discounted payback and savings. Adapted from Duffie and Beckman (2006). This figures only serves as an example for the required cash flow diagram