Please help with part e. Are my other answers right? Problem:
An experiment is conducted at 25 °C and the rate of appearance of the product A2B3(aq) is measured as the concentration of the reactants were varied. Data from the trials are shown below.

Chemical equation: 2A(aq) + 3B(aq) --> A2B3(aq)

Trial | [A] (M) | [B] (M) | Initial Rate of Appearance of A2B3 (M/2)
1 | 0.200 | 0.300 | 5.0x10^-2
2 | 0.200 | 0.900 | 4.5x10^-1
3 | 0.400 | 0.300 | 1.0x10^-1
4 | 0.135 | 0.225 | ???

a. Determine the rate law for the reaction at 25 °C
I got rate=k[A][B]^2
b. Determine the value of k, including units.
I got k=2.8 M^-2 s^-1
c. Determine the rate of Trial 4.
I got 1.9x10^-2 M/s
d. Determine the initial rate of disappearance of A for trial 2.
I got -9.0x10^-1 M/2
e. A possible reaction mechanism has a 1st elementary step as shown below:
A + B --> AB
Could this first step be the rate-determining step? Explain your reasoning.
I don't know how to answer this part.
f. In the reaction mechanism, the compound MnO2 appears. A student makes the claim: "The order of MnO2 must be zero since it does not appear in the overall balanced equation." Do you agree or disagree with the student?
Disagree
g. In trial 1, 10mL of A and 10mL of B are mixed and the reaction goes to completion.
i. Determine the number of moles of B used in the reaction.
0.003 mol B
ii. The reaction vessel is heated and all the water is driven off, leaving only 0.124 grams of A2B3. Determine the molar mass of A2B3.
124 g/mol