Backlog K'rrik, son of yawgmoth can't pay for extort abilities

[sgfalex]

With K'rrik, Son of Yawgmoth and anything with extort such as Crypt Ghast in play; casting a spell generates the extort trigger but you are unable to choose to pay for the ability via black mana paid for by K'rrik's static ability.

Relevant Rulings:

107.4e. Hybrid mana symbols are also colored mana symbols. Each one represents a cost that can be paid in one of two ways, as represented by the two halves of the symbol. A hybrid symbol such as {W/U} can be paid with either white or blue mana, and a monocolored hybrid symbol such as {2/B} can be paid with either one black mana or two mana of any type. A hybrid mana symbol is all of its component colors.

these next ones are rules clarifications straight from the gatherer page for K'rrik, Son of Yawgmoth

8/23/2019 - If a cost contains a mana symbol that may be paid in multiple ways, such as

,

, or

, you choose how you'll pay it before you do so. If you choose to pay

this way, K'rrik's ability allows you to pay life rather than pay that mana.

8/23/2019 - K'rrik's ability lets you pay 2 life for

in any cost you pay, including casting costs, activation costs, and even costs for special actions (such as morph). Any time you pay mana, that's a cost.