Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| PRR Class | Builder’s Model | Build date | Total produced | Wheel arrangement | Service | Power output |
| --- | --- | --- | --- | --- | --- | --- |
| ES6 | SW | 1937 | 12.0 | B-B | Switcher | hp (kW) |
| ES6 | SW1 | 1942–1950 | 85.0 | B-B | Switcher | hp (kW) |
| ES10 | NW2 | 1941–1948 | 32.0 | B-B | Switcher | hp (kW) |
| ES12 | SW7-SW9 | 1950–1953 | 84.0 | B-B | Switcher | hp (kW) |
| ES12 | SW1200 | 1957 | 35.0 | B-B | Switcher | hp (kW) |
| EF15 | F3A,F7A | 1947–1952 | 203.0 | B-B | Freight | hp (kW) |
| EF15 | F3B,F7B | 1947–1952 | 107.0 | B-B | Freight | hp (kW) |
| EPF15 | FP7A | 1952 | 40.0 | B-B | Pass | hp (kW) |
| EPF15 | FP7B | 1952 | 14.0 | B-B | Pass | hp (kW) |
| EP20 | E7A | 1945–1949 | 46.0 | A1A-A1A | Pass | hp (kW) |
| EP20 | E7B | 1945–1949 | 14.0 | A1A-A1A | Pass | hp (kW) |
| EP22 | E8A | 1950–1952 | 74.0 | A1A-A1A | Pass | hp (kW) |
| ERS15 | GP7 | 1952–1953 | 66.0 | B-B | Freight | hp (kW) |
| ERS15ax | SD7 | 1953 | 2.0 | B-B | Freight | hp (kW) |
| ERS17 | GP9 | 1955–1959 | 310.0 | B-B | Freight | hp (kW) |
| ERS17a | SD9 | 1957–1958 | 25.0 | C-C | Freight | hp (kW) |
| EF22 | GP30 | 1963 | 52.0 | B-B | Freight | hp (kW) |
| EF25 | GP35 | 1964–1965 | 119.0 | B-B | Freight | hp (kW) |
| EF25a | SD35 | 1965 | 40.0 | C-C | Freight | hp (kW) |
| EF30a | SD40 | 1966 | 65.0 | C-C | Freight | hp (kW) |
| EF36 | SD45 | 1966 | 65.0 | C-C | Freight | hp (kW) |
| EF20a | GP38 | 1967 | 5.0 | B-B | Freight | hp (kW) |
Question:
What is the PRR class of the freight train built in 1967 with a b-b wheel arrangement?
Answer:
EF20a