It sounds like <em>R</em> is the region (in polar coordinates)
<em>R</em> = {(<em>r</em>, <em>θ</em>) : 2 ≤ <em>r</em> ≤ 3 and 0 ≤ <em>θ</em> ≤ <em>π</em>/2}
Then the integral is
Since she spent $9.72 and deposited $9.72 her bank balance did not change at all. She basically paid off how much she spent on lunch on Wednesday.
Please put more details in the question
Answer:
let x=rate of the rowing team in still water
x+4=rate of the rowing team with current
x-4=rate of the rowing team against current
travel time=distance/rate
..
90%2F%28x%2B4%29=10%2F%28x-4%29
90x-360=10x+40
80x=400
x=5 rate of the rowing team in still water=5 mph
