The patch area in square kilometers is 1.59*10⁻⁹ km₂
Why?
This is an unit conversion problem. We have to convert from cm² to km². We can do that by knowing that there are 100 cm in 1 m, and 1000 m in 1 km, so 100000 cm=1km. Knowing that we can apply the following conversion factor:

Now to convert this value to scientific notation, we have to move the decimal point to the right until we get a whole number, and the exponent of the number 10 is going to be the number of spaces we moved to the right (negative), so the final answer is:

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Answer:
The mixture of B and C will melt as 130 - 139 ºC.
Explanation:
If the melting point (130 - 139 ºC) of a mixture of A and B is lower than the pure substances that is 149 - 150 ºC that means that one of these susbtances is an impurity because reduces the melting point.
If the melting point of the mixture of A and C is the same as the pure substances, we can deduce that they are the same substances, also because the melting point when a substance is pure is just 1 or 2 ºC like in this case.
So in a Mixture of B and C is going to be like the first case of the mixture among A and B, because the B substance is the impurity.
It’s C magnetic field because with the forces of the magnets pushing against each other it gets the engine to start turning the wheels.