Cody has two bags of counters, bag A and bag B.Each of the counters has either an odd number or an even number written on it. There are 10 counters in bag A and 7 of these counters have an odd number written on them. There are 12 counters in bag B and 7 of these counters have an odd number written on them. Cody is going to take at random a counter from bag A and a counter from bag B.
a) Complete the tree diagram.
Harriet also has a bag of counters. Each of her counters also has either an odd number or an even number written on it. Harriet is going to take at random a counter from her bag of counters. The probability that the number on each of Cody's two counters and the number on Harriet's counter will all be even is 3/100.
b)Find the least number of counters that Harriet has in her bag.