John computes the sum of the elements of each of the 15 two-element subsets of $\{1,2,3,4,5,6\}$. What is the sum of these 15 sums?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
John computes the sum of the elements of each of the 15 two-element subsets of $\{1,2,3,4,5,6\}$. What is the sum of these 15 sums?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
105
John computes the sum of the elements of each of the 15 two-element subsets of $\{1,2,3,4,5,6\}$. What is the sum of these 15 sums?
train