Part I

Link to .psd

Link to .psd

Link to .psd

Part II Lab

Original: 1280 x 960, file size: 312k

Thumbnail:
Resized: 150 x 99
Optimization: 60%, 5.67k

Resized: 500 x 375, Unsharp Mask: Amount: 75%, Radius: 1.5 pixels, Threshold: 26 levels
Save for Web: At 100% it's 175.4k
Optimized: 50% to 40.01k

Original: 1189 x 881, file size: 388
Cropped using Crop Tool
Resized to 500 x 376
Optimized: 40k

Thumbnail. Used Transform option this time.
USM: 90, 1.0, 84

Original: 1280 x 960, file size: 1.1m
Cropped with Crop Tool.
Resized 500 x 370.
USM: 80, 1.0, 84
Optimized: 44k

Thumbnail:
150 x 111
Optimized: 30%