Assuming a speed limit is 105 km/hr, what is this in miles per hour

105 km/hr is the same as 65.244 miles per hour.  You can do this by doing unit conversions until you get the satisfied units.  Then you multiply and reduce the fraction.  In this case, the answer is 65.244 miles per hour.

28.6%

Explanation:

The four firm concentration ratio is a matrix that shows how much control the 4 largest firms in a market have.

It is calculated by summing the market share of the four largest firms in the industry.

So calculating for it would be

Four firm concentration ratio = 11.2%(firm A) + 7.7% (firm B) + 5.1% (firm C) + 4.6% (firm D)

= 28.6%

The four-firm concentration ratio for the above industry is 28.6%