Need help with finding mean and standard deviation in rstudio.

questions:

1. how to find the mean of q3?

2. how to find the mean and standarad deviation of q3 for female?

3. find the mean and standard deviation of the difference between pre and post score

table named evalscore:

workshop	gender	q1	q2	q3	q4	pretest	posttest
1	f	1	1	5	5	72	80
2	f	2	1	4	4	70	75
1	f	2	2	4	5	74	78
2	na	3	1	2	4	80	82
1	f	4	5	5	3	75	81
2	m	5	4	2	3	72	77
1	m	5	3	2	4	68	88
2	m	4	5	na	2	71	78
1	m	4	5	na	2	71	78
2	m	2	2	3	1	45	51