For (a), we have
C(12, 7) * (.389)^7 * (.611)^5 = about .09 or about 9/100
For (b), we have
C(12,10) * (.389)^10 * (.611)^2 = .00195
+ C(12,11) * (.389)^11) * (.611)^1 = .000226
+ C(12,12) * (.389)^12) * (.611)^0 = .000012
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about .0022 = about 22/10,000 = 11/5000
