MCGT#9 More Marion History Mystery Cache

This is a two stage multi featuring Ohio Historical Markers. At the posted coordinates you will need to find two numbers and perform some simple math computations to determine the final cache coords. You will be able to drive and park very close to the markers at each stage.

To determine the coordinates to the final you will need to adjust the posted coords as follows:
On the sign find two numbers. Let A = the distance of grassland (in feet) extending east between the road and railway. Let C = the number of species of significant Prairie grasses and flowers in this strip of land.

Then B = (A/10) + 56. Subtract B from the Northing.
Next D = (Cx16) + 4. Add D to the Westing.

At the final you can read some interesting history about the "Marion Engineer Depot."

MCGT #1 - The 29th President - GC3MC16
MCGT #2 - Harding Boyhood Home - GC3MC5Z
MCGT #3 - Marion County Courthouse - GC3MC24
MCGT #4 - Stengel True Museum - GC3MC38
MCGT #5 - OSU & Marion Tech - GC3MC3X
MCGT #6 - Marion Steam Shovel - GC3MC2Y
MCGT #7 - WWII Comes To Marion - GC3MC51
MCGT #8 - Scioto Ordinance Plant - GC3MC5D
MCGT #9 - More Marion History - GC3MC4G
MCGT #10 - Harrison Military Road, War of 1812 - GC3MC6P
MCGT #11 - Pleasant Township Park - GC3MC78
MCGT #12 - The Old Blockhouse - GC3MC7Z
MCGT #13 - Green Camp - GC3MC8D
MCGT #14 - New Bloomington - Farmers Welcome - GC3MCCA
MCGT #15 - Greenville Treaty - GC3MCD2
MCGT #16 - RIP At The Frame - GC3MCE6
MCGT #17 - Oorang Indians - GC3MCEV
MCGT #18 - Marion Quarry Park - GC3MCFM
MCGT #19 - Morral Community Park - GC3MCG0
MCGT #20 - The Lynn School - GC3V9XQ
MCGT #21 - Welcome To Big Island - GC3V9Y9
MCGT #22 - Marion Golfers Relax - GC3V9XY
MCGT #23 - Bonus Cache - GC3TB8B