Design and analysis of algorithms

You are asked to design an algorithm to optimize profit on a stock X.  The following is how the stock has been doing for the last 10 days:

Day 1: $143;

Day 2:  $122;

Day 3:  $121;

Day 4:  $119; 

Day 5:  $147;

Day 6: $170;

Day 7: $172;

Day 8: $180;

Day 9:  $170;

Day 10: $161.

Your algorithm should:

a)  find the lowest price to buy and the highest price to sell. 

b) make the buying date before the selling date

Hint: To make the algorithm more effective you may create two arrays or lists instead of one.