tim began purchasing blt, inc., mutual fund shares several years ago. he has followed a dollar-cost averaging approach by investing $1,000 each year for five years. the following data depicts tim's purchases: year investment share price 1 $1,000 $120 2 $1,000 $100 3 $1,000 $118 4 $1,000 $97 5 $1,000 $130 what is tim's average cost per share? a) $118.23 b) $111.58 c) $106.32 d) $126.10