College football same game spread and total parlay (all-up)

Hi,

just wondering if anyone has a way of fairly accurately estimating the EV for spread and total (college) football parlays in games where the spread and the total is close (within 0 to 14 points of each other), see examples below

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for both examples i will use the same game, details below:

09/20/2014

337 Eastern Michigan: +45 @ +104
338 Michigan State: - 45 @ -122

Total O/U 52: both @ -108
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eg (1)

the parlay of Eastern Michigan +45 and the Under 52 is +292 (on their website they round it DOWN to the next whole number, it should be + 292.88...)

eg (2)

the parlay of Michigan State -45 and the Over 52 is +250 (same as eg 1 above, they round down from what it should be exactly, to the next whole number)
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again the question was how to accurately estimate the EV for this type of situation, as i already 'know' that the chance is between 25% and 50%, and if i had to make a 'ball-park' guess, they would be between 30% and 38% chance of occurring (each parlay)

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thanks in advance