What is the structural formula of 2-methylpropyl 2-methylbutanoate?
CH3CH(CH3)CH2COOCH2CH(CH3)2\text{CH}_3\text{CH}(\text{CH}_3)\text{CH}_2\text{COOCH}_2\text{CH}(\text{CH}_3)_2CH3CH(CH3)CH2COOCH2CH(CH3)2
CH3CH2CH(CH3)COOCH2CH(CH3)2\text{CH}_3\text{CH}_2\text{CH}(\text{CH}_3)\text{COOCH}_2\text{CH}(\text{CH}_3)_2CH3CH2CH(CH3)COOCH2CH(CH3)2
CH3CH2CH(CH3)COOCH(CH3)CH2CH3\text{CH}_3\text{CH}_2\text{CH}(\text{CH}_3)\text{COOCH}(\text{CH}_3)\text{CH}_2\text{CH}_3CH3CH2CH(CH3)COOCH(CH3)CH2CH3
CH3CH2CH2COOCH2C(CH3)3\text{CH}_3\text{CH}_2\text{CH}_2\text{COOCH}_2\text{C}(\text{CH}_3)_3CH3CH2CH2COOCH2C(CH3)3