Need formula that calculates AVG number based on exact criteria

Hi!

I would need your help - is there any formula that could help me to calculate total average number of recruitment days (i'ts one number), but only for "Diana" and "Skipper" (excluding "Jennifer")?

Please see an example:

Recruitment days Responsible
12 Diana
13 Diana
19 Diana
16 Skipper
23 Jennifer
24 Diana
26 Diana
29 Diana
30 Diana
34 Jennifer
36 Skipper
29 Skipper
12 Diana
11 Skipper
1 Skipper
30 Diana
12 Jennifer
16 Jennifer
17 Diana
21 Jennifer


I guess it has something to do with AVG and IF formulas, but I need your help!
Many thanks!

Lindee

Many thanks Richard, you really helped me! :D