Geometric/Arithmatic Series

a)Using the appropriate formula, calculate:

9

Σ

(‐2)*n*5*n*

n

=1

b) A company is considering sending a team of divers, with all the appropriate equipment, down to a famous German U

‐boat wreck. It will cost $560 for the first metre, $640 for the second metre, $720 for the third metre, and so on increasing $80 each time. Using the appropriate formula, determine how much it will cost to reach the U‐boat, which is at a depth of 85 metres?

c) Given that a wealthy historian is willing to pay the company $1,000,000 for any artefacts collected from the U‐boat in b), what will be the profit (loss) to the company if they go ahead with the dive?

The answers I got were:

a) -909090910

b) $333,200

c) $668,800

Did I go wrong? Thanks

Ibrox