Miguel did not focus on differentiation. Differentiation in marketing refers to that thing about your company or product that makes you unique and better than everyone else. Speed2U's competitive advantage is their delivery speed. Miguel should have responded that what makes Speed2U unique is their ability to deliver in 15 minutes or less.
P = $20, the principal in the year 1871.
A = $17,000, the value in the year 2014
t = 2014 - 1871 = 143 years, the duration.
Let r = the yearly return on the investment.
If we assume that the compounding is performed yearly, then
P(1 + r)¹⁴³ = A
That is,
20(1 + r)¹⁴³ = 17000
(1 + r)¹⁴³ = 850
r = 0.0483 = 4.83%
Answer: 4.83%
She spend over her budget/income so she has to owe more money