Assume a pipelined implementation with unbalanced $4$ stages: S$1($stage $1)$ takes $100ns,$ S$2$ takes $200ns,$

S$3$ takes $300ns,$ and S$4$ takes $100ns.$

what is the execution time of $3$ instructions in $ns?$

$*$x Example $-$ If answer is $500\mathrm{.}235$ ns write $500\mathrm{.}24$

$**$ Example $-$ If answer is $600ns$ write $600$

The correct answer is: $1300$