AI doesn't activate first ability of The Underworld Cookbook

[MorihiroS]

Describe the bug
AI doesn't activate first ability of The Underworld Cookbook even if it has 1+ big mana creatures and reanimator spell (like Goryo's Vengeance or Persist) in hands.

To Reproduce
Steps to reproduce the behavior:

1. AI has 3+ untapped lands and The Underworld Cookbook on the battlefield
2. AI has Goryo's Vengeance and Emrakul, the Aeons Torn in hands
3. AI doesn't activate first ability of The Underworld Cookbook to discard Emrakul, the Aeons Torn

Expected behavior
AI should activate first ability of The Underworld Cookbook if it has few lands, 1+ big mana creature and reanimator spell in hands

Desktop
OS: Windows 10
Java Version: 1.8.0_202-b08
Forge Version: 1.6.65-SNAPSHOT-09-06

Screenshots