What if interest rates rise: a mortgage payment's sensitivity

Workflow 5 steps, run in order in one session. Every step was executed against the engine and the output below is what it produced.

Step 1

payment[principal_, rate_, months_] := principal (rate/12)/(1 - (1 + rate/12)^(-months))

No output - this step sets something up for the next one.

Step 2

current = N[payment[400000, 0.065, 360]]

Output

2528.272093971862

Step 3

N[payment[400000, 0.08, 360]] - current

Output

406.7862015456485

Step 4

perPercentagePoint = N[D[payment[400000, r, 360], r] /. r -> 0.065]/100

Output

263.0602719400421

Step 5

Plot[payment[400000, r, 360], {r, 0.03, 0.10}]

Output

-Graphics-

Functions used