Correct! lines that have undefined slopes are always parallel to the y-axis as the change in x is 0. A gradient is calculated by the change in y divided by the change in x and anything divided by 0 is referred to as undefined.
You just do 1x2x3x4 and then that equals 24 so now you have 24 and then you add 4 zeros because their are 4 zeros in the equation so then the final answer is 240000