Answer
The reaction is first order with respect to 1-bromobutane and with respect to methoxide ion.
Rate law is $Rate = k[CH_3O^-][C_4H_9Br]$
Overall order = 2
Work Step by Step
The reaction is first order with respect to 1-bromobutane (because reaction rate triples when we triple its concentration) and with respect to methoxide ion (because reaction rate doubles when we double its concentration).
Rate law is $Rate = k[CH_3O^-][C_4H_9Br]$
Overall order = 1+1 = 2
