Preciso selecionar o valor máximo e o valor minimo de 3 colunas

Preciso selecionar o valor máximo e o valor minimo de 3 colunas, o script sql que estou usando é o seguinte:

Select Id, Min(Valor) from(Select id, valor from((Select Id, Service_Rates_30 as valor from GT_Therapist as a) union (Select Id, Service_Rates_60 as valor from GT_Therapist as B) union (Select Id, Service_Rates_90 as valor from GT_Therapist as c )))Select Id, Max(Valor) from(Select id, valor from((Select Id, Service_Rates_30 as valor from GT_Therapist as a) union (Select Id, Service_Rates_60 as valor from GT_Therapist as B) union (Select Id, Service_Rates_90 as valor from GT_Therapist as c )))

porém a mensagem de erro é a seguinte: Error -2147217900 Incorrect syntax near ')'.alguém pode me ajudar?