Domain: Organic synthesis / HRMS

In an organic transformation, 2-acetylphenyl methyl phthalate is converted to the final product through the following reaction sequence.
Step 1: The starting compound is treated with potassium hydroxide in pyridine under reflux for 30 minutes, resulting in formation of Intermediate A.
Step 2: Intermediate A is then reacted with 2 N hydrochloric acid to afford the desired final product (Compound B).
Determine the exact mass corresponding to the [M+H]+ ion of the final compound (Compound B) as would be observed by high-resolution mass spectrometry.

Grading rubric:
criterion: Correctly identifies the starting material as 2-acetylphenyl methyl phthalate.
weight: 10
criterion: Correctly interprets Step 1 (KOH, pyridine, reflux) as base-promoted cyclization.
weight: 10
criterion: Correctly identifies Intermediate A as 2-(2-hydroxybenzoyl)-1H-indene-1,3(2H)-dione.
weight: 20
criterion: Correctly interprets Step 2 (2N HCl) as acid-promoted intramolecular cyclization.
weight: 10
criterion: Correctly identifies Compound B as indeno[1,2-b]chromene-10,11-dione.
weight: 10
criterion: Correctly assigns the molecular formula of Compound B as C16H8O3.
weight: 20
criterion: Correctly reports the exact m/z value of the [M+H]^+ ion for Compound B as 249.051.
weight: 20

Answer:
m/z 249.051 for [M+H]+