VMware Fusion 7 Yosemite Guest Stuck on 1024x768

I'm running VMware Fusion 7 under OS X Mavericks 10.9.5 with OS X Yosemite 10.10 as my guest OS.  However, the only display resolution I can get is 1024x768!  Does anyone know how I can get a higher resolution?

My host Mac is as follows:

- iMac 27-inch from late 2009

- 2.8GHz Quad-Core Intel Core i7

- 2TB Serial ATA Drive

- 16GB 1066MHz DDR3 SDRAM

- ATI Radeon HD 4850 512MB (2560x1440)

Thanks