Acertain ore yields an average of 64% iron. how much ore is needed to obtain 896 lb of iron?

In this case, the ore yield 64% iron and you need 896 lb of iron. From this description you can get an equation like this:

Iron= iron ore mass * 64%

Then, to get 896 of iron the calculation should be:
Iron= iron ore mass * 64%
896 lb= iron ore mass * 0.64
iron ore mass= 896 lb/ 0.64= 1400lb

The rate law is [B]

Explanation:

In Trials 1 and 2, the concentration of B changes and A is the same so you can see how changes in B affect the rate. In this case, 0.300/0.150=2 and 7.11 x 10^-4 / 3.56 x 10^-4= 2. Since there 2^1=2, we can say that the reaction order of B is 1.

Similarly, if we look at trials 2 and 3, the concentration of B is constant, while A is changing. In this case, the rate has not changed at all with a change in concentration of A, so this means that A has 0 order.

Therefore, the rate law is just [B].