Unless you're able to provide a diagram representing the problem, there's not much I can do so solve this problem.
Note that
1 m = 3.2808 ft
Therefore
1 km = 3280.8 ft
and

Answer: 1.0682 x 10⁵ ft/hr
It is A. Barium
Explanation: I did that already
Answer: 2.58 days
Explanation:
Expression for rate law for first order kinetics is given by:
where,
k = rate constant = ?
t = age of sample = 6 days
a = initial amount of the reactant = 1 g
a - x = amount left after decay process
= 0.2 g
a) to find the rate constant
b) for completion of half life:
Half life is the amount of time taken by a radioactive material to decay to half of its original value.
The half life is 2.58 days