Bob and Dave created a partnership, opening Bars-R-Us downtown San Antonio, Texas, selling beer and wine consumed on the premises. Steve enters the bar and tells Bob "I have three employees that sell smokeless cigarettes (e-cigarettes) for my company. If you allow me to sell the e-cigarettes on your premises for the next 5 years I will give you 10% of the proceeds." Bob says sure and signs an exclusive contract that allows only Steve and his associates to sell e-cigarettes at Bars-R-Us. 

Is Dave liable under the contract to permit Steve to sell the e-cigarettes as a result of Bob's actions?