Answer : C.
3 meters=3000 millimeters
Answer : The metal used was iron (the specific heat capacity is
).
Explanation :
In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.


where,
= specific heat of unknown metal = ?
= specific heat of water = 
= mass of unknown metal = 150 g
= mass of water = 200 g
= final temperature of water = 
= initial temperature of unknown metal = 
= initial temperature of water = 
Now put all the given values in the above formula, we get


Form the value of specific heat of unknown metal, we conclude that the metal used in this was iron (Fe).
Therefore, the metal used was iron (the specific heat capacity is
).
I think it takes about 278g but I'm not 100% sure
The boat is flattened and there is more air against the surface pushing it up but a block has all weight in one place and will just sink<span />
Answer
1.5 miles per hour
hope this helps and have a wonderful day :)