I know that this seems a childish question but i have not been able to find a proper convention that cover all math operations. Obviously the basic is that exponential takes precedence over multiplication (and division) that takes precedence over sum (and difference). A particular case can be the sign "$-$" that indicates both the binary operation of subtraction and the unary operation of negation (sign reversal), since the unary operators should take precedence over the binary operators.
My question is focused about operators like summatory, productory, factorial, gradient, etc...
For example, how the following expression should be evaluated? A or B? $$\sum k!$$ A) $\left(\sum k\right)!$
B) $\sum \left(k!\right)$