The missing length is 12km (i never promised anything xd)
N=11
I’m not 100% sure
Hoped this helped
In descriptive statistics, the interquartile range<span> (</span>IQR<span>), also called the midspread or middle 50%, or technically H-spread, is a measure of statistical dispersion, being equal to the difference between 75th and 25th percentiles... ~ wikipedia
according to Wikipedia and some quick mental math the answer would be four
four is the difference between 14 and 18 which are respectively the 25th and 75th percentiles.</span><span />
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Explanation:</h2><h2 />
The complete question is shown in the figure below. As you can see one square units is well shown in the graph. So we can conclude that the distance between two consecutive points is 1 unit. If so, then we can calculate the area of the parallelogram as follows:

Then, finding CB by Pythagorean Theorem:

And:

Therefore:

Multiplying a negative number and another negative number makes the product positive.
So (-2.1)*(-1.4) = 2.94