The following data represents the prices (in R) of 50 items purchased by a shopper.

Price R	Frequency
0.00 > 20.00	6
20.00 < 40.00	9
40.00 < 60.00	18
60.00 < 80.00	13
80.00 < 100.00	4

Determine the:

1.1 mean price 

1.2 median price. 

1.3 modal price 

1.4 standard deviation