If $3^{}p+3^{4}=90$, $2^{}r+44=76$, and $5^{3}+6^{}s=1421$, what is the product of $p$, $r$, and $s$? (2013 AMC 8 Problem, Question \#15) 
选项为:A:$$27$$  B:$$40$$  C:$$50$$  D:$$70$$  E:$$90$$  请回答其中一个选项.